Within the recent past an experimental imaging radar system has been developed which produces high resolution target images of ships and aircraft. A wideband frequency stepping technique is used to achieve high range resolution. Coherent signal processing produces high resolution in the cross range dimension.
Prior to this invention the controller for the radar system used unprogrammable hard wired components. The hard wired controller produced 1 to 512 discrete frequency pulses increasing monotonically with a constant step size of 1.08 MHz.
A microprocessor-based controller has been developed to improve control capability of the radar imaging system. The microprocessor-based controller provides for variable step size (0.1 through 99.9 MHz), more steps (up to 5,000) and programmable frequency sequences. The microprocessor is also used in making out-of-band and transmitter duty cycle limit calculations. The new controller provides the advantages of improved operational ease, extensive flexibility for image quality investigations, improved electronic counter countermeasures (ECCM), and the additional flexibility in programming various frequency sequences for image quality investigations. The new control system provides programming options for investigating image quality as a function of sample rate or of transmitted bandwidth.
Briefly, the invention generates control signals to a radar. These signals cause the radar to change frequency, pulse repetition frequency (PRF), and monitor transmitter duty cycle limits under the control of an internal stored program executed by a commercial microprocessor. A critical feature of the invention is due to the necessary control functions being completed within the pulse repetition time (as short as 20 microseconds).